Would be more likely because Bilic is also Croatian, makes a big difference if your coach can speak your native language and can understand some of the cultural differences.
One of the reasons that Deulofeu chose Everton for his loan was because of Martinez's Catalonian links.
Yes, he will be using his contacts in the National team to push him to select West Ham.
While Martinez will be using his contacts in Barca, like Mark Hughes.
Stoke will be all over him.